I couldn't think how to word the title to read what I wanted it to mean. I've only changed the oil in my truck once or twice since I've had it so while I was in walmart buying oil I decided to double check to be sure I got the right filter. I was pretty sure my '99 silverado took an AC Delco pf46e filter (again just wanted to double check). The book says a '99 silverado 5.3L takes a pf61. I knew this wasn't right so I called autozone and they said it showed 2 for that vehicle. pf46 (that I remember) and the pf61. He couldn't tell me what the difference was, but did point out that one is longer than the other. I remember buying the longer one for my old k1500, but the pf46 that I'd been buying for this silveraydo was the shorter one. The question is: why the addition of another filter all of a sudden? Maybe it just took them this long to finally update the book at walmart? This site shows both: http://www.autozone.com/external-eng...ers=4294853337

1. Always use the longer filter whenever you have the option.
2. You will NOT find a quality oil filter at most Walmart stores - if you're lucky they might have a Purolator. Mostly Fram, (the WORST option you can choose, TRUST ME, many thousands of mechanics agree), or AC/Delco.

Catalog info on filters has always been sketchy, been that way forever.
Back in the heyday of the older GM V-8's, mid 1960's to late 1990's, (All engine sizes: 283, 327, 350, 400 Small-blocks and 396, 402, 427, 454 Big-Blocks), they all used the same basic oil filters, (AC/Delco PF25 or PF35). Most catalogs always showed only the PF25, which was the short filter, except for the trucks with same engines, they listed the PF35. I found this idiotic, as you could put the longer, better PF35 on about 95% of the Chevy cars. Same thing happens these days. Always use the longer filter. Especially on these LS engines, the filters are ridiculously small, about 1/4 the size of the old PF35.
And I agree with j_cAT - Go with a better quality filter. Wix brand are as good as you can get, and Wix also makes the NAPA "Gold" house brand for them. Most chains like O'Reilly and AutoZone used to keep Wix in the back, but they are finally putting them out on the public shelves now. Wix P/N 51522 for your truck, and I highly recommend using synthetic oil, (Not "high mileage", just regular Full Synth, like Valvoline or Mobil), and also the Wix 51522XP oil filter, which is a couple dollars more, but made specifically for Synthetic oils. Delco used to be good, but they have cheapened them up so bad, no longer a steel core, now they use some ridiculously weak plastic cage that can collapse easily in cold weather driving.